Conventionally, an electrostatic induction power generator is known in which a pair of substrates configured to be able to reciprocate relative to each other while maintaining a state in which the substrates face each other are provided, a plurality of electrets are arranged in a row on one of the pair of substrates, and a plurality of pairs of electrodes are arranged in a row on the other one of the pair of substrates. According to the electrostatic induction power generator, when the pair of substrates move relative to each other, an electrostatic capacitance between one electrode of a pair of electrodes and the electret changes and also an electrostatic capacitance between the other electrode of a pair of electrodes and the electret changes, so that a difference of the electrostatic capacitances is output as electric power.
In the electrostatic induction power generator, a distance between the electret and a pair of electrodes in a direction in which the pair of substrates face each other largely affects power generation performance. Therefore, it is important to improve the accuracy of the distance to improve the power generation performance. Therefore, conventionally, a technique is known which includes a member for adjusting a distance between a support member supporting one of a pair of substrates and a support member supporting the other substrate (see Japanese Patent Application Laid-Open No. 2009-148124 1).
The technique will be described with reference to FIG. 12. FIG. 12 is a schematic cross-sectional view of an electrostatic induction power generator according to a conventional example. The electrostatic induction power generator 200 includes a pair of substrates (referred to as a first substrate 220 and a second substrate 230 respectively). A plurality of electrets are arranged in a row on the first substrate 220 and a plurality of pairs of electrodes are arranged in a row on the second substrate 230. The first substrate 220 is supported by a first support member 211 and the second substrate 230 is supported by a second support member 212. The first substrate 220 is configured to be able to move in a direction in parallel with a surface of the substrate. The first substrate 220 and the second substrate 230 can move relative to each other while maintaining a state in which the first substrate 220 and the second substrate 230 face each other.
The electrostatic induction power generator 200 is provided with adjustment members 240 for adjusting a distance between the first support member 211 and the second substrate 230 fixed to the second support member 212. According to the technique, in a state in which the adjustment members 240 are disposed between the first support member 211 and the second substrate 230 fixed to the second support member 212, the adjustment members 240, the first support member 211, the second support member 212, and the second substrate 230 are fixed by bolts 250, so that the distance is adjusted.
However, as described above, the power generation performance is affected by the distance between the electret and a pair of electrodes in a direction in which the pair of substrates face each other. If it is possible to ignore the variation of the thickness of the electret and the variation of the thickness of the pair of electrodes, the distance between the surfaces of the pair of substrates facing each other affects the power generation performance.
Therefore, in the conventional example described above, the error propagation to the distance that affects the power generation performance is large. Specifically, in the conventional example described above, the distance between the first support member 211 and the second substrate 230 is adjusted. Therefore, a dimensional error that affects the accuracy of the distance between the surfaces of the first substrate 220 and the second substrate 230 facing each other includes a dimensional error of the adjustment members 240, a dimensional error of the first support member 211, and a dimensional error of the thickness of the first substrate 220.
Here, in the electrostatic induction power generator, the distance between the electret and a pair of electrodes in a direction in which the pair of substrates face each other is, for example, about 70 μm and the distance between the surfaces of the pair of substrates facing each other is, for example, about 85 μm. On the other hand, the tolerance of a glass substrate on which the electret and the like are formed is generally ±50 μm with respect to a desired thickness.
Therefore, in the conventional example described above, the dimensional error of the thickness of the first substrate 220 affects the accuracy of the distance between the surfaces of the pair of substrates facing each other, so that it takes time and cost to adjust the distance. Thus, for example, it is necessary to prepare a plurality of types of adjustment members 240 whose lengths are different from each other or adjust the length of the adjustment member 240 for each product.